Performing Department
(N/A)
Non Technical Summary
Biological nitrogen fixation in root nodules of soybean helps reduce the need for expensive, energy-intensive, and environmentally damaging synthetic nitrogen fertilizers. Nodule nitrogen supply peaks during early reproductive stages (R1-R3) and declines thereafter, whereas grain nitrogen demand increases in the later reproductive stages (R5-R7). Therefore, high-yielding soybean varieties take up nitrogen from the soil, depleting soil nitrogen reserves that would otherwise be available for the future crops necessitating research to increase nodule nitrogen supply in later reproductive stages. We hypothesize that soybean genotypes with a higher number of nodules with delayed maturation can continue to fix nitrogen at these reproductive stages and help meet nitrogen needs in a sustainable manner. Prior results and preliminary data from the PD's laboratory as well as those from other research suggest that altering the balance between two plant hormones auxin and cytokinin can lead to higher nodule numbers with delayed maturity. This research project will (1) evaluate genome sequences of 1,110 accessions from the USDA soybean germplasm collection to identify natural genetic variants in genes associated with auxin and cytokinin biosynthesis, (2) validate their roles thorough genome editing and laboratory analysis, and (3) characterize soybean germplasm with specific genetic modification for optimal nitrogen fixation. The accessions or derivatives including knowledge would help develop soybean varieties with optimal nitrogen fixation that do not deplete soil nitrogen or required additional nitrogen fertilizer application.
Animal Health Component
0%
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Biological nitrogen fixation provides only 50 to 60% of soybean's nitrogen needs. Nodule nitrogen supply declines during later reproductive stages R5 and R7 presumably due to nodule senescence. This leads to depletion of soil nitrogen by soybeans or in some cases necessitates application of additional nitrogen by soybean producers at these stages. We hypothesize that soybean genotypes with a higher number of nodules with delayed maturation can continue to fix nitrogen at these reproductive stages and help meet nitrogen needs in a sustainable manner. Prior findings suggest that reducing auxin output and/or increasing cytokinin output can lead to higher nodule numbers. The proposed project is expected to identify auxin and cytokinin genes responsible for nodule numbers, delayed nodule maturity and senescence in soybean.Optimizing nodule number, maturation and senescence provides the nitrogen fixed by the nodule available to the plant during the reproductive stages of soybean development, thereby helping sustainably meet soybean nitrogen needs.The objectives in this project are:1. To identify natural genotypic variation in auxin and cytokinin biology genes using 1000 soybean genomes data.2. Generating and characterizing CRISPR edits in hairy roots targeting components of auxin and cytokinin biology genes.3. Phenotyping selected natural genetic variants and genome-edited lines for hormone responses, nodulation, and nitrogen fixation.
Project Methods
For Objective 1, SnpEff tool (abbreviation for SNP effect) annotates the identified variants as "modifier" (representing mutations found in intergenic regions) "low" effect (leading to synonymous mutations), "moderate" effect (resulting in non-disruptive alterations in the protein structure) and "high" effect (causing disruptive changes to protein), considering the kind and placement of genetic variation. In Objective 2, Genome editing will be performed for corresponding genotypes or lines with "high level" genetic variations. Edited hairy roots will be tested for hormone responses and nodulation parameters nodule numbers and nitrogen fixation capacity and compared to "unedited" control roots using statistical analysis to determine significant changes if any. For Objective 3, Selected genotypes/lines with "high level" genetic variations from SnpEff analysis will be tested for nodulation efficiency using nodule number, nodule maturation times, nitrogen fixing capacity during reproductive stages. Statistical analysis will be used to determine significant changes in these parameters to evaluate the effect of genetic variation on nodule development and nitrogen fixation.